Kommentar zu Dewarim 27:12

לברך את העם [THESE SHALL STAND UP …] TO BLESS THE PEOPLE — The procedure was as is found in Treatise Sotah 32a: Six tribes ascended the top of Mount Gerizim and the other six the top of Mount Ebal, the priests, the Levites and the Ark remaining below in the midst (i.e. in the valley between). The Levites turned their faces towards Mount Gerizim and began to recite the blessing: “Blessed be the man that does not make any graven or molten image etc.”, and both these and those (the tribes on Mount Gerizim and those on Mount Ebal) answered “Amen”! Then they turned their faces towards Mount Ebal and began to recite the curse, saying: “Cursed be the man who maketh any graven [or molten image]” — and so in the case of all of them (the curses set forth here) till the last: “Cursed be he that does not uphold [all the words of this law to do them]” (cf. Rashi on Deuteronomy 11:29).

'אלה יעמדו לברך וגו, according to the plain meaning the tribes mentioned forthwith were to confirm what the Levites said by answering Amen. The Levites, when pronouncing the respective blessings or curses, would face Mount Gerizim when intoning the blessings, and Mount Eyval when intoning the curses. (Sotah 32)

אלה יעמדו לברך. “These are to stand (on Mount Gerizim) to bless the people.” Our sages (in Sotah 32) state that the blessing consisted of: “Blessed be the man who has not made a hewn image, etc.,” whereas the curse consisted of the words spelled out in verses 15-26. Six tribes whose ancestors were sons of either Leah or Rachel stood on the mountain facing which the blessing was pronounced, whereas the sons of Zilpah and Bilhah as well as Reuven and Zevulun stood on Mount Eyval, in whose direction the curses were pronounced in order to complete the number of six tribes required to stand there. The reason the tribe of Shimon was also associated with the tribes in whose direction the blessings were pronounced was that the Torah lists here eleven different curses and the Torah wanted to avoid pronouncing a curse in his direction. Moses decreed that all the tribes receive a blessing, seeing, however, that the tribe of Shimon was not deserving of a blessing on account of Zimri its leader who had caused so much death amongst his own people, he wanted to at least not make it appear as if he were being cursed, i.e. of associating the word ארור with something pronounced in his direction. Had he allowed this to occur Shimon would have been beyond redemption (Rashi in the name of Rabbi Moshe Hadarshan).
Our sages in Sifri Vezot Habrachah item 348, claim that the blessing of the tribe of Yehudah contained within it an allusion to a blessing for the tribe of Shimon, seeing that Shimon’s tribal territory was described as an enclave within that of the tribe of Yehudah. The fact that the tribe of Reuven was placed on the mountain in whose direction the curses were pronounced does not constitute something negative against this tribe. I believe that this was the final part of the apology for the episode described in the Torah involving Reuven and Bilhah. Cursing someone who sleeps with the wife of his father (verse 20) was meant to draw our attention to the fact that actually Reuven had never been guilty of that sin. This is why the sages of the Midrash (Yalkut Shimoni Vayechi 157) claim that Yaakov, his father, had already told him that the stigma which had attached itself to him on account of what is described as יצועי עלה in Genesis 49,4 would not be totally removed from him until the one (leader Moses) of whom the Torah had written עלה, “arise!” would come. As soon as Moses arranged for the tribe of Reuven to take his place among the tribes facing the pronouncement of the curses, Reuven’s stigma had been completely wiped out. What occurred at Mount Eival enabled our sages to say (Shabbat 58) that anyone accusing Reuven of having committed the sin of sleeping with his father’s wife is in error.
What precisely was the arraignment of the respective tribes like on these two mountains? Our sages in Sotah 32 have described it in these words: “6 tribes ascended the top of Mount Gerizim whereas 6 other tribes ascended the top of Mount Eyval. The priests and Levites took up their position in the valley separating these two mountains. The priests would surround the Holy Ark. The Levites would surround the priests. The Israelites would be on either side of them (on the mountain). This is the meaning of ‘and all of Israel its elders and law-enforcers and judges would stand on either side of the Holy Ark facing the Priests who carried the Ark of the Covenant’ (Joshua 8,33). The Priests and Levites turned their faces in the direction of Mount Gerizim, beginning to recite the blessing, commencing with the words: ‘blessed be the man who has not constructed a hewn image, etc.’ The tribes standing on both mountains would respond by chanting “Amen.” The blessings were followed by the curses, a similar procedure being followed.” After completion of this ceremony they brought the stones and built an altar of them, covering the altar with plaster and inscribing on it the entire Torah in seventy languages. This is proven by verse 8, i.e. באר היטב. After this they took the stones with them returning to their assigned place for the night (Gilgal). Thus far the wording of the Mishnah. [The difficulty in all this is the distance from Gilgal to Mount Eival and the impossibility to accomplish all this within a day without miracle. (Compare the various commentators of the Mishnah), Ed.]